LATEST DEVELOPMENTS
— Officials say the bombs consisted of kitchen pressure cookers packed with nails, ball bearings and other shrapnel.
— Both bombs were stuffed inside duffel bags and left on the ground at the race.
— President Barack Obama calls the bombings an act of terrorism but says investigators do not know who is behind them.
— An 8-year-old boy, a 29-year-old woman and a graduate student from China died in the blasts.
— The number of injured rises to more than 170.
— Obama will visit Boston on Thursday for an interfaith service.
Pressure-cooker bombs
The explosives used in the Boston Marathon bombing were crude devices often called pressure cooker bombs, according to a person briefed on the investigation.While the devices have been frequently used in Afghanistan, India and Pakistan, in recent years they have also shown up in plots in the U.S. and France.Explosives typically are placed inside a pressure cooker — a commonplace cooking utensil in many countries — and the device is then detonated using everyday electronic equipment such as digital watches, garage door openers, cellphones or pagers. Al-Qaida affiliates have provided training and manuals on how to build such devices.
Recent container bombs
February 2013: A bomb hidden in a pressure cooker explodes inside a restaurant in northern Afghanistan, killing five people.
October 2012: French police find bomb-making materials in an underground parking lot near Paris as part of a probe into an attack on a kosher grocery. The discovery includes bags of potassium nitrate, sulfur, headlight bulbs and a container used as a make-shift pressure cooker.
May 2012: U.S. jurors hear that explosives experts had found a pressure cooker containing smokeless gunpowder and other material in the Texas motel room of a soldier accused of planning to blow up Fort Hood military troops and other personnel.
May 2010: One of the three devices used in the attempted bombing in New York's Times Square was a pressure cooker, according to a joint FBI and Homeland Security intelligence report issued in July 2010.
March 2010: Suspected militants attack the U.S.-based Christian aid group World Vision in northwestern Pakistan, killing six Pakistani employees. Officials say the attackers remotely detonated a pressure-cooker bomb.
March 2006: A series of bombings kill 20 people in India. One bomb — at a temple in the northern city of Varanasi where five people died — was placed in a pressure cooker and detonated by a timing device.
December 2004: Ten accused Islamic militants are convicted for their roles in a plot to blow up a Christmas market in the eastern French city of Strasbourg on New Year's Eve 2000. Authorities say the group had planned to blow up containers packed with explosives, a technique they allegedly learned in Afghan camps.
The bombs that ripped through the Boston Marathon crowd appear to have been fashioned out of ordinary kitchen pressure cookers, packed with nails and other lethal shrapnel, and hidden in duffel bags left on the ground, investigators and others close to the case said Tuesday.
President Barack Obama branded the attack an act of terrorism, but said that it was unclear if it had been carried out by an individual or a group, foreign or domestic. The FBI vowed to “go to the ends of the Earth” to find out who did it.
Scores of victims remained in Boston hospitals, many with serious injuries, a day after the twin explosions near the marathon’s finish line killed three people, wounded more than 170 and reawakened fears of terrorism. A 9-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.
Officials found that the bombs consisted of explosives put in common 1.6-gallon pressure cookers, one containing shards of metal and ball bearings, the other packed with nails, according to a person close to the investigation who spoke on condition of anonymity because the investigation was still going on. Both bombs were stuffed into duffel bags, the person said.
At a news conference, Richard DesLauriers, the FBI agent in charge in Boston, confirmed that investigators had found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI for analysis at Quantico, Va.
Pressure-cooker explosives have been used in international terrorism, and have been recommended for lone-wolf operatives by Al-Qaida’s branch in Yemen.
But information on how to make the bombs is readily found online, and U.S. officials said Americans should not rush to judgment in linking the attack to overseas terrorists.
DesLauriers said that there had been no claim of responsibility for the attack, and that the range of suspects and motives was “wide open.”
Throughout the day, he and other law enforcement authorities asked members of the public to come forward with any video or photos from the marathon or anything suspicious they might have witnessed, such as hearing someone express an interest in explosives or a desire to attack the marathon, or seeing someone carrying a dark heavy bag at the race.
“Someone knows who did this,” the FBI agent said.
The bombs exploded 10 or more seconds apart, tearing off victims’ limbs and spattering streets with blood, instantly turning the festive race into a hellish scene of confusion, horror and heroics.
The blasts killed 8-year-old Martin Richard of Boston, 29-year-old Krystle Campbell of Medford, Mass., and a third victim, identified only as a graduate student at Boston University.
Doctors who treated the wounded corroborated reports that the bombs were packed with shrapnel intended to cause mayhem.
“We’ve removed BBs and we’ve removed nails from kids. One of the sickest things for me was just to see nails sticking out of a little girl’s body,” said Dr. David Mooney, director of the trauma center at Boston Children’s Hospital.
Obama plans to visit Boston on Thursday to attend an interfaith service in honor of the victims.
He has traveled four times to cities reeling from mass violence, most recently in December after the schoolhouse shooting in Newtown, Conn.
In the wake of the attack, security was stepped up around the White House and across the country. Police massed at federal buildings and transit centers in the nation’s capital, critical response teams deployed in New York City, and security officers with bomb-sniffing dogs spread through Chicago’s Union Station.
Homeland Security Secretary Janet Napolitano urged Americans “to be vigilant and to listen to directions from state and local officials.” But she said there was no evidence the bombings were part of a wider plot.
Pressure-cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 intelligence report by the FBI and the Homeland Security Department. One of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the report said.
“Placed carefully, such devices provide little or no indication of an impending attack,” the report said.
Investigators said they have not yet determined what was used to set off the Boston explosives
Typically, these bombs have an initiator, switch and explosive charge, according to a 2004 warning from Homeland Security.
“We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice,” the FBI’s DesLauriers said.
The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any part in the Boston Marathon attack.
Al-Qaida’s branch in Yemen gave a detailed description of how to make a bomb using a pressure cooker in a 2010 issue of Inspire, its English-language online publication aimed at would-be terrorists acting alone.
In a chapter titled “Make a bomb in the kitchen of your mom,” it says “the pressurized cooker is the most effective method” for making a simple bomb, and it provides directions.
Naser Jason Abdo, a former U.S. soldier, was sentenced to life in prison last year after being convicted of planning to use a pair of bombs made from pressure cookers in an attack on a Texas restaurant frequented by soldiers from nearby Fort Hood. He was found with the Inspire article.
Investigators are also combing surveillance tapes from businesses around the finish line and asking travelers at Boston’s Logan International Airport to share any photos or video that might help.
“This is probably one of the most photographed areas in the country yesterday,” said Boston Police Commissioner Edward Davis. He said two security sweeps of the marathon route had been conducted before the bombing.
Boston police and firefighter unions announced a $50,000 reward for information leading to arrests.
Obama said officials do not know who carried out the attack or why — “whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual.”
But he said “any time bombs are used to target innocent civilians, it is an act of terror.” And he declared: “The American people refuse to be terrorized.”
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